MICROSCALE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY ELECTROSPRAY TANDEMMASS-SPECTROMETRY ASSAY FOR CYCLOSPORINE-A IN BLOOD

To facilitate quantitative analysis of cyclosporin A in low volume blo od samples we developed a sensitive and specific microscale reversed-p hase HPLC-electrospray tandem mass spectrometry assay. Blood samples ( 100 mu l) were prepared by acetonitrile precipitation and C-18 solid-p hase extraction. Detection was by multiple-reactant monitoring. The me thod was linear over the range 5-1000 mu g/l (greater than or equal to 0.997) with accuracy between 95.4 and 102.0% over this range. Total i mprecision was 11.1% at 10 mu g/l and 2.8% at 800 mu g/l. Absolute rec overy of cyclosporin A and internal standard was 72.5 and 73.3%, respe ctively. When this method was evaluated against a conventional HPLC wi th UV detection, in patient samples, they were interchangeable (y=0.98 8x+10.0, r=0.996). This HPLC--ESI-MS-MS method will be applicable to t herapeutic monitoring in paediatric transplant patients and multiple p oint pharmacokinetic studies in animals and humans. (C) 1998 Elsevier Science B.V.